1. Field of the Invention
In circulatory disturbances therapy using rheologically active substances is gaining in importance, especially when a retrogression of rheological blockages is no longer possible. Rheologically active substances improve the blood flow. If the rheological component predominates as compared with other effects on the circulatory system, these substances which stimulate the circulation are referred to as "rheologica" (Radke et al., 1983). An increased flow capacity increases the flow of blood through the flow paths (microcirculation) and thereby also the oxygen supply to the tissues. This is particularly the case when the blood vessels can no longer continue to be supplied at the pathological initiation site and therefore the vasomotor reserve is exhausted.
2. Background Information
.alpha.-lipoic acid is referred to chemically as 1,2-dithiolane-3-pentanoic acid, 5-(1,2-dithiolane-3-yl)-valeric acid or 5-3-(1,2-dithioanyl)pentanoic acid. .alpha.-lipoic acid possesses a chiral C atom, occurs in two enantiomeric forms and is found physiologically in plants, in bacteria and in the mammalian organism. It has the function of a coenzyme in mitochondrial multienzyme complexes such as, for example, those of pyruvate dehydrogenase, of .alpha.-ketoglutarate dehydrogenase and of the dehydrogenase of the branched-chain amino acids. During metabolism .alpha.-lipoic acid can be converted from the oxidized form (disulphide bridge) to the reduced dihydro form having two free --SH groups. Both forms have a distinct antioxidizing action (for example, Kuklinski et al., 1991; Packer, 1993). The redox pair dihydrolipoic acid/.alpha.-lipoic acid moreover has metal-chelating properties. In the Federal Republic of Germany .alpha.-lipoic acid has been in use since 1966 as a medicine for the treatment of diseases of the liver, in fungal poisoning and in peripheral polyneuropathies. From knowledge of this antioxidizing action, general reference is made in DE-OS 41 38 040 A1 to a compound which catches free radicals and possesses thiol functions. The claim relates to solutions for the perfusion, conservation and reperfusion of organs and does not relate to the present invention, because here a new action in a new application has been found over and above the known antioxidizing property.
The SU Patent 1 769 865 A1 relates to the use of compounds including .alpha.-lipoic acid for the phenomenological improvement of the blood circulation and, more precisely, to the enlargement of the blood stream through the large vessels of the uterus and to the decrease of the volumetric variables in the region of the chorion in placental insufficiency.
A compound preparation containing Ginkgo biloba extract is also described in EP-OS 0 326 034 for the prophylaxis and treatment of circulatory disturbances (Koltringer, 1989).